Predjama Castle, known locally as Predjama Grad, sits an hour southwest of Slovenia’s capital, (the impossible-to-pronounce) Ljubljana. Originally built in the 12th Century on top of a cave, the Castle was expanded and added onto during the 16th Century, and the efforts of those labors are largely what we see today.

Appearing to hang in the middle of a 403-foot-tall limestone cliff, Predjama Castle was carved into the side of the rock and has no man-made rear walls: the vertical face of the cliff serves as those walls. Today, visitors to the Castle can tour the grounds and the inside of the building — as well as explore the caves and underground river below the architectural marvel. To get a sense of the unique “fit” the castle has with the cliff, check out Slovenia Landmarks, which has an excellent VR tour of the Castle and in its interior.

If you go to Predjama, aim for August, when locals stage the Erasmus Knights’ Tournament. During the event, men and women in period constume engage in medieval games played during the 16th Century — complete with archery, swordplay, jousting, and eating and drinking contests.